Provide an easy way to install optional dependencies

README.md

@@ -31,10 +31,14 @@ The following dependencies are required:
 
 and the following are optional:
 
-* [PyAVM](http://astrofrog.github.io/pyavm/)
-* [pyregion](http://pyregion.readthedocs.org/)
-* [Python Imaging Library](http://www.pythonware.com/products/pil/) (PIL)
+* [PyAVM](http://astrofrog.github.io/pyavm/) 0.9.4 or later
+* [pyregion](http://pyregion.readthedocs.org/) 2.0 or later
+* [pillow](https://pypi.org/project/Pillow/) 4.0 or later
 
 You can install APLpy with:
 
     pip install aplpy
+
+If you want to install all optional dependencies, you can do:
+
+    pip install aplpy[all]

docs/index.rst

@@ -30,6 +30,17 @@ is consistent with Matplotlib, then we recommend you use `WCSAxes`_ directly. If
 you have a FITS file and just want to make it into a plot in a couple of lines,
 then APLpy is the package for you.
 
+Installing APLpy
+================
+
+You can install APLpy with pip using::
+
+    pip install aplpy
+
+To include all optional dependencies, you can do::
+
+    pip install aplpy[all]
+
 Using APLpy
 ===========
 

setup.cfg

@@ -22,7 +22,7 @@ auto_use = True
 [metadata]
 package_name = aplpy
 description = The Astronomical Plotting Library in Python
-long_description =
+long_description = The Astronomical Plotting Library in Python
 author = Thomas Robitaille and Eli Bressert
 author_email = thomas.robitaille@gmail.com, elibre@users.sourceforge.net
 license = MIT
@@ -35,3 +35,4 @@ version = 0.0.dev
 
 [options.extras_require]
 docs = sphinx-astropy
+all = pyregion>=2.0; pillow>=4.0; pyavm>=0.9.4